This invention relates to a tread pattern on a pneumatic tire for passenger cars, which displays an excellent stability when the car runs on a road surface having grooves which extend in the direction in which the car runs.
There are some expressways and general roads which are provided in the surfaces thereof with longitudinal grooves extending substantially in parallel with one another in the direction in which a car runs and in a regularly-spaced manner (for example, at intervals of 19 mm), so as to prevent the travelling stability of a car from being spoiled when the road surface is moistened.
A conventional tire for passenger cars, which has in its ground-contacting surface linear grooves extending in the circumferential direction of the tire, has in general an excellent travelling stability on a moistened road surface as compared with other types of tires. However, in such a tire for passenger cars, which has linear grooves mentioned above, a tottering phenomenon called groove wandering occurs while the car runs on such a road surface, so that the linear travelling stability of the car is liable to be spoiled.
Accordingly, in order to improve the travelling stability of the tire, the tread pattern formed on the ground-contacting surface of the tire is designed so that the edges of the tread pattern and the longitudinal grooves in the road surface are not aligned with each other (not less than two edges of the tread pattern do not simultaneously engage the grooves in the road surface), and the rigidity of the edges of the tread pattern is set to a low level. Nevertheless, the groove wandering cannot sufficiently be suppressed.